Power factor correction is required to counteract any phase difference between the alternating voltage of the mains and the alternating current drawn from the mains by a reactive load. When an alternating current runs through a reactive load, a phase of the alternating current may be shifted by the reactive load, creating a phase difference between the alternating current and the alternating voltage. The power required by a load can be split into real power and reactive power, wherein the real power results from the resistive part of the load and the reactive power results from the reactive part of the load. In the pure reactive part of the load, the phase difference of the voltage and current is 90 degrees and so there is no net power flow, although these phase shifted voltages and currents run through the electrical components and wires. So the electrical components must be chosen such that they can withstand these phase shifted voltages and currents. Furthermore, the phase shifted voltages and current contribute to the energy loss in the system. As a consequence, the power factor representing a relationship between the reactive power and an apparent power should be substantially unity.
Power factor correction may be done passively and actively. In a passive correction of the power factor, the reactive character of the load is compensated for by adding capacitors and inductors such that the load behaves substantially as a resistive load.
Alternatively, the power factor may be corrected actively. A general configuration of a known active power factor control circuit is to use a power converter in a boost configuration also indicated as boost converter. This boost converter is arranged between a rectifier which rectifies the mains voltage and a load. In the known power factor control circuit the boost converter comprises a series arrangement of an inductor and a switch arranged between the nodes of the rectified mains. A series arrangement of a diode and an output capacitor being arranged parallel to the switch. The boost converter used as a power factor control circuit attempts to maintain a constant DC-voltage on its output while drawing a current from the mains that is substantially always in phase with the mains voltage and substantially at the same frequency as the mains voltage. In such a configuration, a further power converter may be arranged between the load and the known power factor control circuit to convert the boosted output power of the known power factor control circuit into the required voltage for the load.
A drawback of the known power factor control circuit is that the reliability of the known power factor control circuit is not good enough.